CHAP. III. DELTA AND ALLUVIAL PLAIN OF THE NILE. 35 



of the amount of sediment formed in a century, which they 

 suppose not to exceed on the average five inches. When the 

 waters subside, this thin layer of new soil, exposed to a hot sun, 

 dries i-apidly, and clouds of dust are raised by the winds. The 

 superficial deposit, moreover, is disturbed almost everywhere 

 by agricultural labors, and, even were this not the case, the 

 action of worms, insects, and the roots of plants would sufiice 

 to confound together the deposits of two successive years. 



All the remains of organic bodies, such as land-shells, and 

 the bones of quadrupeds, found during the excavations be- 

 longed to living sjDccies. Bones of the ox, hog, dog, dromedary, 

 and ass were not uncommon, but no vestiges of extinct mam- 

 malia. No marine shells were anywhere detected ; but this 

 was to be expected, as the borings, though they sometimes 

 reached as low as the level of the Mediterranean, were never 

 carried down below it, — a circumstance much to be regretted, 

 since where artesian perforations have been made in deltas, 

 as in those of the Po and Ganges, to the depth of several 

 hundred feet below the sea-level, it has been found, contrary 

 to expectation, that the deposits passed through were fluvia- 

 tile throughout, implying, probably, that a general subsidence 

 of those deltas and alluvial formations has taken place. 

 Whether there has been in like manner a sinking of the land in 

 Egypt, we have as yet no means of pi'oving; but Sir Gardner 

 Wilkinson infers 'it from the position in the delta on the shore 

 near Alexandria of the tombs commonly called Cleopatra's 

 Baths, which cannot, he says, have been originally built so as 

 to be exposed to the sea which now fills them, but must have 

 stood on land above the level of the Mediterranean. The same 

 author adduces, as additional signs of subsidence, some ruined 

 towns, now half under water, in the Lake Menzaleh, and 

 channels of ancient arms of the Nile submerged with their 

 banks beneath the waters of that same lagoon. 



In some instances, the excavations made under the super- 



